CO2 activation to produce useful products for chemical processes through a wide variety of approaches have been reported for CO2 utilization to control greenhouse gas emissions. Three different methods for converting CO2 to CO or synthesis gas using Group II metal ferrites. CO and synthesis gas are useful precursors for various chemical processes and are used as a fuel for energy production.
Process 1: Catalytic Dry Reforming
Catalytic dry reforming illustrated in reaction 1 is a process that converts two greenhouse gases, methane and carbon dioxide into a useful product, synthesis gas.CH4+CO2⇄2CO+2H2 ΔHR=+205 kJ mol−1 at 298 K  [1]
Natural gas which mainly consist of methane is an abundant resource. Natural gas is flared in refineries and is necessary to develop cost effectives routes to convert natural gas to useful products. Steam methane reforming (SMR) shown in reaction [2] is the commercial process to produce synthesis gas and H2 from methane.CH4+H2O⇄CO+3H2ΔHR=247 kJ mol−1 at 298 K  [2]
However, the SMR process has many disadvantages: the H2/CO ratio obtained in the product stream is very high (>3) for direct downstream conversion processes; and excess steam is introduced requiring additional energy for steam generation.
The production of syngas from CO2 and CH4 via dry reforming as in reaction [1] is a promising alternative and has received industry attention as it offers several advantages such as mitigation of greenhouse gases CO2 and methane and converting these gasses into valuable syngas with a H2/CO ratio 1 which may be used to produce valuable chemicals downstream.
A technoeconomic analysis (See Kartick Monda, Sankar Sasmal, Srikant Badgandi, Dipabali Roy Chowdhury & Vinod Nair, Dry reforming of methane to syngas: a potential alternative process for value added chemicals—a techno-economic perspective, Environ Sci Pollut Res (2016) 23:22267-22273 DOI 10.1007/s 11356-016-6310-4) indicates that dry reforming of natural gas/CO2 is a competitive process with lower operating and capital costs in comparison with steam reforming assuming a negligible cost of CO2 import.
Various catalysts have been used for the dry reforming process (See Jean-Michel Lavoie, Review on dry reforming of methane, a potentially more environmentally-friendly approach to the increasing natural gas exploitation, Frontiers in chemistry, published: 11 Nov. 2014 doi: 10.3389/fchem.2014.00081, and WO Patent No. 2014/1645592 A1 to Meissner et al, titled Systems and methods for generating carbon dioxide for use as a reforming oxidant in making synthesis gas).
Supported noble metals (Pt, Pd, Rh, Ru) have shown promising results for methane dry reforming but are very expensive. Non-noble transition metals such as Ni, Co, Fe which are relatively less expensive have been used and Ni has shown the most promising results. However, Ni based catalysts tend to deactivate and there are environmental concerns with Ni. Therefore, it is necessary to develop more effective catalysts.
There is a need for catalysts used in a methane dry reforming process that improve performance, are inexpensive and environmental safe.
Process 2: Chemical Looping Dry Reforming
In this process reported in the literature conversion of CO2 to CO is accomplished using CO2 as an oxidant in a process called “Chemical Looping Dry Reforming” (CLDR) (See Vladimir V. Galvitaa, Hilde Poelmana, Christophe Detavernierb, Guy B. Marin, “Catalyst-assisted chemical looping for CO2 conversion to CO”, Applied Catalysis B: Environmental 164 (2015) 184-191; and WO Patent No. 2014/016790 A1 to Al-Shankiti et al, titled Catalyst for thermochemical water splitting).
In the CLDR process, carbon dioxide is used for oxidizing a reduced oxygen carrier instead of using air as an oxidant as used in conventional chemical looping combustion (CLC) or in place of steam in the chemical looping steam reforming process. Either methane or coal may be used as the fuel for initial reduction of the oxygen carrier (MeO) to produce reduced metal (Me) while oxidizing the fuel. Instead of combusting the fuel fully, this initial reduction reaction of MeO may also be used to produce a useful product such as CO or synthesis gas from fuel as shown in reactions [3], [4] and [5]. Then the reduced oxygen carrier (M) is oxidized with CO2 to form CO and MeO as shown in reaction [6].
Reduction of oxygen carrier (MO):3MeO+2C=3Me+CO+CO2  [3]MeO+2C+H2O=Me+2CO+H2  [4]MeO+CH4=Me+CO+2H2  [5]
Oxidizer:Me+CO2=MeO+CO  [6]
Since CO2 is a highly stable molecule and a weak oxidant, selection of an oxygen carrier to perform the oxidation reaction is critical for this process. Stability of oxygen carriers at extended high-temperature cyclic operation and carbon formation during oxidation with CO2 are additional challenges. Additionally, slower oxidation kinetics using CO2 in place of oxygen (air) that is used in CLC need to be addressed.
Thermodynamic studies have shown that Fe-based carriers were the most suitable oxygen carriers but the reactivities of Fe based structures were low. Finding a suitable oxygen carrier to convert CO2 to CO has been a challenge.
There is a need for oxygen carriers for chemical looping dry reforming to convert CO2 to CO.
Process 3: Conversion of CO2 to CO Via Gasification of Coal with CO2 with an Oxygen Carrier
Coal gasification with CO2 as illustrated in reaction [7] has been reported to produce CO. (See Muhammad F. Irfan, Muhammad R. Usman b, K. Kusakabe, Coal gasification in CO2 atmosphere and its kinetics since 1948: A brief review, Energy 36 (2011) 12e40)C+CO2→2CO Δ Hr=+172 mJ/kmol at 25 C and 1 atm  [7]
Alkali and alkali earth metals in the carbonate forms and iron have been used to promote the reaction [7]. Evaporation of these promoters and processing of coals with promoter solutions have been challenging issues for the process.
There is a need for promoters for the CO2 conversion to CO via coal gasification.